Hydroelectric Energy

Hydropower is a clean, renewable energy source.Billions of people rely on hydropower today. Hydroelectricity is made from running water.The word "hydro" is "water" in Greek.Originally water mills, people have previously used them to grind grain and cut lumber.It uses falling water to turn a turbine to make electricity.The first United States Hydroelectric Power Plant was built on the Fox River in 1882.It is in Appleton, Wisconsin.The largest plant in the world is The Three Gorges Dam, which is located over the Yangtze River in China.It has 26 large turbines that produce more than a billion watts per kilowatt-hour.A large dam is built over a river to block water in a reservoir.It is built in an area of the river that has a large drop of elevation.Water is stored behind the dam in a reservoir.When water is ready to be let through the dam, it travels through a penstock and then through a turbine.The water rotates the turbine and makes electricity.The water then travels down through the rest of the river.Engineers can control how much water flows through the dam at a time.This is called the intake system.When more energy is needed, more water flows through the dam.When less energy is needed, less water flows through the dam.Large, fast flowing rivers produce the most energy. They can also be placed over waterfalls, but a river is most traditional.As with other power sources, there is always a little twist.Like all renewable energy sources, it seems, there is always a little of Carbon Dioxide that sneaks through.When generating electricity, hydropower does not release Carbon Dioxide.However, the dams do have a footprint.This footprint comes from when the dam is being constructed and the slow decomposition of the dam.One dam will emit between 10 and 30 grams of Carbon Dioxide for each kilowatt-hour of energy produced.This has to do with how the reservoir is made.Inside of the water that is being held back, plants decompose slowly.This produces methane, one of the greenhouse gases.It also cuts down on the amount of plants in the world, which means less carbon dioxide will be absorbed by plants.Also, the dams are made of cement.When cement is cooling, it emits Carbon Dioxide in large amounts.Sometimes, as well, the cement needs to be carried to the site of its installation.This means more Carbon Dioxide is being emitted from the transportation process. Despite these drawbacks, it is said that the initial Carbon Dioxide emissions are offset by the years of zero-carbon electricity production.